Manufacture of probe unit having lead probes extending beyond edge of substrate

ABSTRACT

A sacrificial layer is formed in a recess of a substrate, and leads extending from the substrate into an area of the sacrificial layer are formed. A cut is formed from the bottom surface of the substrate, the cut extending from the bottom surface to the area of the sacrificial layer via the substrate, then the sacrificial layer is removed. A probe unit can be obtained having the leads whose front portions extend beyond the edge of the substrate. A through conductor may be formed in a through hole formed in a substrate. Leads may be formed on a photosensitive etching glass substrate to thereafter selectively etch the chemically cutting type glass.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and claims priority of Japanese patentapplication No. 2001-086267, filed on Mar. 23, 2001, the whole contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

A) Field of the Invention

The present invention relates to a method of manufacturing a probe unithaving leads disposed in parallel at a small pitch, each lead extendingbeyond the edge of a substrate to form an elastic beam. The probe unitis used, for example, for a conduction test of electrodes of asemiconductor integrated circuit, a liquid crystal panel or the like.

B) Description of the Related Art

A conduction test of a semiconductor integrated circuit, a liquidcrystal panel or the like is performed in order to check whether thetest sample operates normally satisfying the specification. Thisconduction test is performed, for example, by pressing the front end ofa probe unit against electrodes disposed in parallel at the edge of aglass plate of a liquid crystal panel. It is therefore necessary thatthe front portions of leads of the probe unit formed on a substrate formelastic beams.

The pitch of the electrodes disposed at the edge of a liquid crystalpanel is becoming smaller. The pitch of elastic beams of the frontportions of leads of a probe unit is required correspondingly small.

The pitch of electrodes is presently 0.1 mm. A probe unit to be usedwith such electrodes is difficult to be formed with a punching machine.From this reason, etching or plating has been used for forming a probeunit.

Probe unit manufacture methods are disclosed, for example, inJP-A-8-015318. According to one method, two substrates are abuttedtogether and a number of leads are grown by plating on the surface ofthe substrate to be disposed in parallel and traversing the twosubstrates. Next, one of the two substrates is removed from the leadsextending on the surface of the substrate so that the front portions ofleads extend beyond the edge of the other substrate to form elasticbeams. According to the other method, a number of leads are grown byplating in parallel on the surface of one substrate. Next, the endportion of the substrate is cut so that the front portions of leadsextend beyond the edge of the remaining substrate to form elastic beams.

Another probe unit manufacture method is disclosed in JP-A-7-199219.According to this method, a silicon oxide film is formed on a siliconsubstrate. The silicon oxide film is partially removed by etching toexpose the surface of the silicon substrate on which elastic beams ofprobes are later formed. A metal film having a predetermined pattern isformed on the exposed silicon surface and oxide film. Leads of a probeunit are grown on the metal film by plating. Next, the exposed siliconsubstrate is removed by anisotropic etching so that the front portionsof the leads extend beyond the edge of the remaining substrate to formelastic beams.

The first method disclosed in JP-A-8-015318 teaches some device ofmaking a coupling force of a plated layer to a contact lead region ofthe substrate different from a coupling force to an elastic lead regionof the substrate. However, there remains some problem that some tightcontactness is required between a plated underlayer and the substrate inthe elastic lead region when the plated underlayer is formed and whenthe plated layer is grown and that some peeling property is requiredwhen the substrate is removed from the leads. If the coupling force ofthe plated layer is too small, the plated layer is separated from thesubstrate because of stress generated during plating. The shape of afine probe may be deformed or damaged. If the coupling force is high,the function of removing the substrate from leads becomes low and theleads may be deformed following the deformed shape of the substrate. Ifthe single substrate is used and this substrate cannot be cutcompletely, elastic beams extending beyond the edge of the remainingsubstrate cannot be formed. It is necessary to cut the substrate withoutdamaging the leads. This cutting is very difficult and there is a highpossibility of damaging leads when the substrate is cut.

In a practical case, the substrate is cut to such a depth reaching nearthe leads so that the cutting blade does not contact the leads. Afterthis cutting, the substrate is bent downward or upward about the cut toremove the end portion of the substrate. Since the cut had a finitedepth, when the substrate was bent upward, the break positions becameirregular because of the cut depth. Further, the substrate moves thelead front portions upward so that some elastic beams were deformed.

The irregularity of break positions was bigger when the substrate wasbent downward than when it was bent upward. The lengths of elastic beamswere irregular and the loads necessary for a predetermined bendingamount were not able to be controlled. A bending work was not stable sothat large forces were applied to some leads some of which weredeformed.

The method described in JP-A-7-199219 requires to anisotropically etchthe end portion of the substrate to form elastic beams. Therefore, thesubstrate is limited only to a silicon substrate. The insulating filmsuch as a silicon oxide becomes essential. Various other substratesrequested by users cannot be adopted.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofmanufacturing a probe unit having elastic beams extending beyond theedge of a substrate by using any type of substrates without damagingleads, the method providing a proper fine pitch of leads and reliablysupporting the leads on the substrate.

According to one aspect of the present invention, there is provided amethod of manufacturing a probe unit having leads whose front portionsextending beyond an edge of a substrate, the method comprising a step offorming a recess in a surface layer of a substrate; a step of forming asacrificial layer filled in the recess; a step of forming a number ofleads on the surface of the substrate, the leads being disposed inparallel and extending into an area of the sacrificial layer; a step offorming a cut extending from a bottom surface of the substrate into thesacrificial layer; and a step of removing the sacrificial layer.

According to another aspect of the invention, there is provided a methodof manufacturing a probe unit having leads whose front portionsextending beyond an edge of a substrate, the method comprising: a stepof forming a through hole through a substrate; a step of forming asacrificial layer filled in the through hole; a step of forming a numberof leads on the surface of the substrate, the leads being disposed inparallel and extending into an area of the sacrificial layer; and a stepof removing the sacrificial layer.

According to another aspect of the invention, there is provided a methodof manufacturing a probe unit having leads whose front portionsextending beyond an edge of a substrate, the method comprising the stepsof: (a) applying a ultraviolet ray to a partial surface area of aphotosensitive etching glass substrate; (b) forming a number of leads onthe surface of the substrate, the leads being disposed in parallel andextending from a ultraviolet ray unradiated area into a ultraviolet rayradiated area; and (c) etching the glass substrate in the ultravioletray radiated area.

Leads can be formed by plating growth at a very fine pitch and with highprecision. The thickness necessary for elasticity of elastic beams canbe obtained sufficiently. Since the leads are properly supported by thesubstrate and/or the sacrificial layer in the recess, a proper pitch canbe set. If the substrate is cut to form elastic beams by using a cutextending from the substrate bottom surface to the area of thesacrificial layer, physical force is not applied to the leads when thesubstrate is cut. A substrate part is separated by removing thesacrificial layer in the recess so that leads are not damaged when thesubstrate part is separated. Substrate part separation may be performedby removing the sacrificial layer in the through hole or etching achemically cutting type glass substrate. Also in this case, leads arenot damaged when the substrate part is separated.

A substrate to be used is not limited to a special substrate, but anysubstrate used by general probe units may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a substrate having a recess in asurface layer thereof, a plated underlayer formed on the whole surfaceincluding the recess, and a plated film formed on the whole surface.

FIGS. 2A and 2B are a plan view of the substrate having metal left onlyin the recess and a flat whole surface including the metal surface, anda cross sectional view taken along line IIB—IIB.

FIGS. 3A and 3B are a plan view of the substrate with the metal only inthe recess, the substrate having a predetermined probe metal patternformed by plating, and a cross sectional view taken along lineIIIB—IIIB.

FIGS. 4A and 4B are a plan view of probes and a cross sectional viewtaken along line IVB—IVB.

FIG. 5 is a cross sectional view showing a substrate having a throughhole in which metal paste is filled.

FIG. 6 is a cross sectional view of a substrate having a through hole inwhich a sacrificial layer is formed and a flat whole surface includingthe sacrificial layer surface.

FIGS. 7A and 7B are a plan view of leads formed on the substrate havingthe sacrificial film in the through hole, and a cross sectional viewtaken along line VIIB—VIIB.

FIG. 8 is a cross sectional view of a probe obtained by a methodincluding a through hole forming process.

FIG. 9 is a cross sectional view illustrating exposure of ultravioletrays toward a photosensitive etching glass substrate.

FIG. 10 is across sectional view of a lead formed on the substrate whichwas partially exposed with ultraviolet rays, the lead extending from theultraviolet ray unradiated area to the ultraviolet ray radiated area.

FIG. 11 is a cross sectional view of a probe unit having elastic beamsextending beyond the edge of a crystallized glass substrate.

FIG. 12 is a cross sectional view of a substrate having conduction holesreaching the bottom surface of the substrate, leads being formed on thesubstrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described with reference to theaccompanying drawings.

FIGS. 1 to 4B are diagrams illustrating an embodiment of the invention,and FIGS. 5 to 8 are diagrams illustrating another embodiment of theinvention.

A substrate 1 of a probe unit of each embodiment is not limited to aparticular substrate, but a glass plate, a synthetic resin plate, aceramic plate, a silicon plate, a metal plate or the like may be used.Of these plates, insulating substrates including a glass substrate and aceramic substrate such as alumina are preferably used. If a conductivesubstrate such as a metal substrate is used, an insulating layer isformed on the substrate on the side where a recess to be described belowis formed.

A recess 2 is formed on one surface side of the substrate. It ispreferable to form the recess 2 straight and parallel to one side of thesubstrate. The recess 2 has a predetermined depth and width andtraverses the substrate. The recess may be formed not traversing thesubstrate and having a length at least longer than the length of a finalprobe unit, and at a later process the substrate region without therecess is cut to form the recess traversing the substrate.

It is preferable to set the depth of the recess 2 to 0.05 to 3.0 mm andthe width to 0.2 to 5 mm.

The recess is filled with a sacrificial layer. The material of thesacrificial film may be metal, resin such as epoxy and urethane, orinorganic material such as inorganic salt. Inorganic salt may be calciumcarbonate.

The thickness of the sacrificial layer 4 is required to be deeper thanthe depth of the recess. The thickness is preferably about 0.05 to 0.4mm, although it depends upon the thickness of the substrate and thedepth of the recess.

In the following description, the sacrificial layer is made of a metalfilm by way of example.

As shown in FIG. 1, a plating underlayer 3 is formed by sputtering onthe whole surface of the substrate with the recess 2. A sacrificiallayer 4 is formed on the plating underlayer 3 by plating metal. Metal tobe plated is metal, e.g., copper, different from the metal of a probe.

If copper is used as the metal to be plated, for example, chromium issputtered as a tight contact layer and then copper is sputtered onchromium.

In this specification, the tight contact layer and upper sputter layerare collectively called a plating underlayer. The plating underlayerused for forming a metal sacrificial layer in the recess is called arecess plating underlayer 3. Without forming the plating underlayer, thesacrificial layer of metal may be formed by electroless plating.

If the sacrificial layer is made of metal, the cross sectional shape ofthe recess at its opposing end portions is preferable a smooth arcshape. The radius of the arc shape is preferably larger than the depthof the recess. If the cross sectional shape of the recess is a rectanglehaving a bottom surface and vertical side walls, voids may be formed inthe sacrificial layer during plating growth of metal from the recessplating underlayer on the bottom surface and side walls. If the shape ofthe recess has the arc shape, voids are difficult to be formed in themetal layer in the recess. Next, the plated surface is polished to leavethe metal layer 4 only in the recess 2 and expose the substrate 1 in theother area, as shown in FIGS. 2A and 2B. The whole polished surface ispreferably flat including the surface of the metal layer 4.

If the substrate is made of conductive material, after an insulatinglayer is formed on the substrate surface side on which a recess isformed, the recess is formed and the recess plating underlayer is formedon the whole substrate surface. Next, a metal layer is formed, and thesurface thereof is polished to leave the metal layer only in the recessand expose the insulating layer on the whole surface excepting thesurface of the metal layer in the recess.

If the sacrificial layer is made of epoxy resin or urethane resin, thesubstrate made of glass, ceramic, metal or the like is used so that thesacrificial layer can be selectively removed at a later process. In thiscase, the cross sectional shape of the recess is not limited to the arcshape, but the shape may be a rectangle constituted of the bottomsurface and side walls.

Resin is filled in the recess to the position higher than the recess andhardened. Thereafter, polishing is performed to planarize the wholesubstrate surface, to leave the resin only in the recess, and to exposethe substrate in the other area.

For example, if epoxy resin is used, this resin can be hardened by aheat treatment at 150° C. The time required to form the sacrificiallayer of resin can be shortened considerably as compared to thesacrificial film formed by plating.

If the sacrificial film is made of inorganic salt such as calciumcarbonate, powders are filled in the recess while taking care in notforming voids or dents, and pressed. Thereafter, the surface is polishedto leave the inorganic sacrificial layer only in the recess.

Next, a plating underlayer (hereinafter called a probe platingunderlayer) 5 is formed on the whole polished surface. Then, a resistpattern is formed having openings corresponding to the leads of probes.The plating underlayer is exposed only in the openings. The resistpattern has preferably such a shape so that leads are disposed inparallel at the same pitch along a direction perpendicular to thelongitudinal direction of the recess.

The front portion of each lead of the probe is positioned on thesacrificial layer 4, and the remaining portion of the lead is positionedonly on one side of the substrate remote from the front portion.

The exposed surface of the probe plating underlayer 5 with the resistpattern is subjected to plating to grow and form leads 6 by using knownFe, Ni plating liquid such as sulfuric acid based liquid.

In forming leads, known pattern forming methods can be used. Forexample, the probe plating underlayer 5 having the probe pattern may beformed, a metal film of the probe underlayer may be formed on the wholesubstrate surface and patterned by photolithography, or conductive pastemay be printed on the substrate surface.

Next, after the resist pattern is removed, the probe plating underlayerexcepting those formed with the leads 6 is removed by milling. With theabove processes, the probe unit can be formed having the leads 6disposed in parallel on the substrate 1 with the sacrificial layerfilled in the recess.

The thickness of each lead is preferably about 10 μm to 80 μm.

FIG. 3A is a plan view of the probe unit formed in the above manner.

FIG. 3B is a cross sectional view taken along line IIIB—IIIB.

Plating metal is preferably nickel, nickel alloy such as NiW and NiFe ormetal glass so that each lead of the probe can have proper rigidity andelasticity.

As shown in FIG. 3B, a cut 7 is formed through the substrate 1 to apredetermined depth of the sacrificial layer 4 as shown by a line D—D.The cut 7 is formed from the bottom surface of the substrate 1 at theposition in the range of the whole width of the lead 6 and in the rangeof the sacrificial layer. The cut 7 reaches the predetermined depth ofthe sacrificial layer 4 and does not cut the whole depth of thesacrificial layer 4 in the recess. Although this cut 7 partitions thesubstrate, the substrate cannot be separated into two parts because thesubstrate is attached to the sacrificial layer 4 in the recess and theleads 6.

As the sacrificial layer in the recess is removed, the substrate isseparated into two parts. Therefore, as shown in FIGS. 4A and 4B, thefront portion of each lead 6 extends beyond the edge of the substrate toform an elastic beam 8, and the other portion thereof is firmly coupledto the substrate. A probe unit can therefore be obtained whose leads aredisposed in parallel at a predetermined pitch.

The direction and shape of the cut along the substrate thicknessdirection may be set as desired.

If the sacrificial layer is made of metal, it can be removed by etching.

If the sacrificial layer is made of resin, it can be removed by solventsuch as hot N-methylpyrrolidone, by ashing or by dry etching. If thesacrificial layer is made of inorganic salt such as calcium carbonate,it can be removed by nitric acid or the like.

With the above-described manufacture method, the cut does not extend tothe position abutting the lead 6 of the probe and a physical force isnot applied such as a peeling force between the leads 6 and substrate 1.Accordingly, a probe having leads reliably disposed at a small pitch canbe obtained by patterning and plating growth without damaging leads.

EXAMPLE 1

In one surface layer of a glass substrate of 76.2 mm square and 0.66 mmin thickness, a recess having a width of 5 mm, a length of 76.2 mm and adepth of 0.3 mm was formed in parallel to one side of the substrate. Thecross sectional shape of the recess at opposing end portions had asmooth arc shape having a radius of 0.5 mm. Chromium as a tight contactlayer was sputtered on the surface of the substrate on the recess side,and copper as a plating underlayer was sputtered on the tight contactlayer. Copper was plated to a thickness of about 0.35 mm.

The substrate was roughly polished by using abrasive grains having adiameter of 3 μm and 1 μm, and then finely polished by using abrasivegrains having a diameter of 0.5 μm. The substrate was planarized byremoving the metal layer on the substrate excepting the metal layer inthe recess. Voids did not exist in the plated copper in the recess.

On the whole surface of the planarized substrate, a probe platingunderlayer of Ti/NiFe was formed by sputtering. On this probe platingunderlayer, a resist pattern was formed having openings in the areascorresponding to probes. Each opening extended from an upper area of oneside of the substrate outside of the recess to an upper area of thecopper plated layer. Each opening was disposed perpendicular to thelongitudinal direction of the recess. A number of openings were disposedat a fine pitch.

An NiFe layer was plated to a thickness of about 30 μm on the probeplating underlayer in each opening.

This substrate was immersed into an ultrasonic vessel to remove theresist pattern by N-methylpyrrolidone. The whole substrate was subjectedto milling by using argon gas to remove the probe plating underlayer andleave probes.

A cut was formed from the bottom surface of the substrate (surface notformed with the probes) to a predetermined depth of the metal layer inthe recess at a position near one end portion of the recess on the sidewhere the leads extend on the substrate. The cut extended in parallel tothe recess longitudinal direction. The cut did not reach the uppersurface of the metal layer.

The metal layer was removed by copper etchant, and the substrate notcoupled to the probes was dismounted. Chromium of the tight contactlayer was removed by chromium etchant. A probe unit was obtained havingthe front portions of the leads extending beyond the edge of thesubstrate to form elastic beams and the other portions firmly coupled tothe substrate.

Another embodiment of the invention will be described.

A through hole is formed through the substrate in an area where thefront portions of all leads are to be disposed in parallel. The throughhole is not formed in the opposite side areas where no lead exists. Thethrough hole has such a shape that the substrate is not separated intotwo parts.

The through hole may be formed: by forming through holes in ceramicsheets still not baked by using a punching machine, laminating as manyceramic sheets as necessary, and then baking the ceramic sheets; byforming a through hole in a baked ceramic sheet by using laser, sandblast or the like; by forming a through hole by etching using a resistpattern; or by forming a through hole in a metal substrate by cuttingand forming an insulating film on the substrate surface and the innerwall of the through hole.

As shown in FIG. 6, a sacrificial film 4 is formed in the through hole.The sacrificial film may be formed by filling metal paste such as copperpaste in the through hole, or by filling resin or inorganic material inthe through hole similar to the embodiment described earlier.

The sacrificial film made of metal paste will be described by way ofexample.

As shown in FIG. 5, metal paste 9 is filled in the through hole. Themetal paste 9 contains solvent. As the metal paste 9 filled in thethrough hole is heated, the solvent is evaporated so that thesacrificial layer made of metal can be formed. Since the metal pastecontracts when it changes to metal, excessive metal paste is filled inthe through hole to such an extent that the metal paste is swelled asshown in FIG. 5. As shown in FIG. 6, the substrate having the throughhole filled with metal paste is heated to form a sacrificial layer 4made of metal. Overflowed metal is removed by polishing so that themetal is filled in the whole area of the through hole and no metalexists in the area outside the through hole.

The metal paste may be filled in the through hole from the upper surfaceside of the substrate, by covering the bottom surface of the substratewith a tape or the like. If metal paste having a sufficiently highviscosity, the metal paste may be filled in the through hole withoutusing the tape.

The amount of metal paste may be set so that the through hole is notcompletely filled with metal when the metal paste is changed to metal.In this case, dents in the through hole are filled with plated metalwhich is formed to such an extent that the plated metal is swelled overthe through hole. The top and bottom surfaces of the substrate arepolished so that the metal is filled in the whole area of the throughhole and no metal exists in the area outside the through hole.

If the sacrificial layer is made of resin, excessive resin is filled inthe through hole to such an extent that the resin is swelled over thethrough hole, because when the resin is hardened, it contracts. Afterthe resin is hardened by a heat treatment or the like, the top andbottom surfaces are polished.

Inorganic material such as calcium carbonate does not contract. Afterinorganic material is filled in the through hole, the inorganic materialis pressed without forming dents in the through hole.

Leads of probes are formed on the surface of the substrate with thesacrificial layer filled in the through hole. The lead forming method ofthe above-described embodiment can be applied.

FIG. 7A is a plan view of the substrate formed with leads and FIG. 7B isa cross sectional view along line VIIB—VIIB shown in FIG. 7A.

The sacrificial layer 4 in the through hole of the substrate formed withthe leads is removed. After or before the sacrificial film is removed,the opposite side areas of the substrate are cut in parallel to theleads, for example, along lines F and G shown in FIG. 7A traversing thethrough hole.

If the sacrificial film 4 is removed after the substrate is cut, thesubstrate is separated into two parts. The front portion of each lead 6extends beyond the edge of the substrate 1 to form an elastic beam 8 andthe other portion is firmly coupled to the substrate. A probe unithaving leads disposed in parallel at a predetermined pitch can thereforebe obtained.

If the sacrificial film is removed before the substrate is cut, elasticbeams extend over the through hole. The substrate is then cut to obtaina probe unit.

FIG. 8 is a cross sectional view of the obtained probe unit.

EXAMPLE 2

Through holes of 5 mm×10 mm were formed through ceramic substrates notbaked each having a thickness of 100 μm by using a punching machine.Twelve ceramic substrates were laminated. The through hole of theceramic lamination substrate was filled with conductive copper paste(product name: CF-2800 manufactured by Harima Chemicals Inc.). Thiscopper paste contains 20 vol % solvent. Since the copper paste contractswhen it is heated, excessive copper paste was filled in the through holeto such an extent that the copper paste is swelled over the throughhole. The substrate was placed in an oven and heated to evaporate thesolvent. The copper was completely filled in the through hole. The topand bottom surfaces of the substrate were polished. The metal layer wascompletely filled in the through hole, and overflowed metal in the areaoutside the through hole was removed to expose the ceramic substrate.

Leads extending above the through hole were formed on the substrate inthe manner similar to Example 1.

The opposite side areas of the substrate were cut in parallel to theleads along lines F and G traversing the through hole outside the leads.A unit having two substrate parts coupled by the metal layer in thethrough hole was obtained.

This copper layer was etched in the manner similar to Example 1 toobtain a probe unit having elastic beams extending beyond the edge ofthe substrate.

A still further embodiment will be described.

In this embodiment, a substrate made of photosensitive etching glass isused.

If ultraviolet rays are applied to photosensitive etching glass and aheat treatment is performed, fine crystals are precipitated. Asolubility speed of the region with precipitated crystals, relative todilute hydrofluoric acid, becomes very large as compared to that of theregion with no precipitated crystals, allowing to selectively andchemically cut the glass.

As shown in FIG. 9, ultraviolet rays are applied to a photosensitiveetching glass substrate 10 in an area other than the area where leadscoupled later to the substrate are left.

The substrate 10 has an ultraviolet ray radiated area 10 a and anultraviolet ray unradiated area 10 b.

As shown in FIG. 10, a number of leads are disposed in parallel on thesubstrate 10, the leads extending from the ultraviolet unradiated area10 b to the ultraviolet radiated area 10 a. The longitudinal directionof each lead is set, for example, perpendicular to the boundary linebetween the ultraviolet ray radiated and unradiated areas.

Metal having a good tight contactness to the glass substrate such as Tiis used as the material of the probe plating underlayer for leads. Theother points are similar to the first embodiment.

As shown in FIG. 11, the glass in the ultraviolet unradiated area isetched and removed by dilute hydrofluoric acid. A probe unit havingleads extending beyond the edge of the glass substrate in theultraviolet ray unradiated area can therefore be obtained. Thissubstrate is baked for 2 to 3 hours at 800 to 900° C. to change thesubstrate to crystallized glass so that the mechanical strength andthermal conductivity can be improved. A probe unit having leadsextending beyond the edge of the crystallized glass substrate can beobtained.

EXAMPLE 3

Photosensitive etching glass was used as a substrate. By shielding oneend area of the substrate, ultraviolet rays were applied to the otherarea by using an exposure machine with a ultra high pressure mercurylamp as a light source. Here the ultraviolet rays may include G line(436 nm), I line (365 nm), and/or H line (405 nm). Ti and then Ni weresputtered to the whole surface of the substrate to form a probe platingunderlayer.

Resist was coated on the substrate, prebaked, exposed, hardened,developed and washed to form a resist mask having openings in areascorresponding to leads. On the plating underlayer exposed in theopenings, an NiW layer was plated to a thickness of 30 μm. Next theresist was removed by ashing and the exposed probe plating underlayerwas removed by milling.

The ultraviolet ray radiated area of the substrate was etched by 5-6%hydrofluoric acid, and washed by pure water. The substrate was baked toform crystallized glass. A probe unit having leads extending beyond theedge of the crystallized glass substrate was obtained.

FIG. 12 shows another modification. Through conductors are formed in aphotosensitive etching glass substrate 10 so that electrodes can be ledfrom the leads to the bottom surface of the substrate. Ultraviolet raysare applied to areas 12 led to the bottom surface, and the substrate isbaked for about 30 minutes at 550 to 600° C. to precipitate crystals inthe radiated area.

This crystal precipitated area is chemically cut (etched) by dilutehydrofluoric acid to form holes through the substrate. Silver or copperpaste is filled in each hole in a manner similar to the processdescribed with FIG. 5. The substrate is then baked to fill the wholethrough holes with metal.

Similar to the embodiment shown in FIGS. 10 and 11, leads are formed.Namely, ultraviolet rays are applied to the area of the substrate wherethe front portion of each lead is exposed, to form a ultraviolet rayradiated area 10 a. Leads are formed each being connected to the metallayer 12 filled in the through hole and each extending from theultraviolet ray unradiated area 10 b to the ultraviolet ray radiatedarea 10 a. Thereafter, the ultraviolet ray radiated area 10 b ischemically cut. In this manner, a probe unit can be obtained in whichleads are guided to the bottom surface of the substrate to be connectedto a wiring unit.

The present invention has been described in connection with thepreferred embodiments. The invention is not limited only to the aboveembodiments. It is apparent that various modifications, improvements,combinations, and the like can be made by those skilled in the art.

1. A method of manufacturing a probe unit having leads whose frontportions extending beyond an edge of a substrate, the method comprisingthe steps of: forming a recess in a surface layer of a substrate;forming a sacrificial layer in the recess; forming a number of leads onthe surface of the substrate, the leads being disposed in parallel andextending into an area of the sacrificial layer; forming a cut extendingfrom a bottom surface of the substrate into the sacrificial layer; andremoving the sacrificial layer.
 2. A method according to claim 1,wherein the sacrificial layer is made of metal, resin or inorganicmaterial.
 3. A method according to claim 1, wherein the sacrificiallayer forming step, comprises: depositing the sacrificial layer both inthe recess and on a surface of the substrate surrounding the recess; andremoving part of the sacrificial layer to leave the sacrificial layer inthe recess.
 4. A method according to claim 3, wherein the sacrificiallayer is first deposited on the entire upper surface of the substratesurrounding the recess and then all of the sacrificial layer locatedoutside of the recess is removed.